1. Field of the Invention
The present invention relates to a magnetic recording medium such as a magnetic tape and magnetic disc, in which a hexagonal system ferrite powder is used as a recording element.
2. Description of the Prior Arts
Requirement for a high density recording of a magnetic recording medium increases year by year. A horizontal recording medium in which acicular magnetic powder is orientated in a magnetic layer has a disadvantage that a rotational demagnetization significantly increases as a recording density is increased. At present, therefore, a vertical magnetic recording medium in which signals are recorded in a vertical direction to a magnetic layer has been developed.
As a magnetic layer formed in such a vertical magnetic recording medium, a layer which is formed by painting platelet particles of hexagonal system ferrite powder, orientating them in parallel to a medium surface is considered to have better properties, such as productivity and durability, than a thin metal layer consisting of a magnetic metal such as Co-Cr.
However, a conventional magnetic recording medium using the hexagonal system ferrite powder has a fatal disadvantage that it has an unsatisfactory storage property since an output of recorded signals attenuates, namely so called "demagnetization by cooling" occurs, when the recording medium is subjected to a low temperature and reproduced at room temperature after signals are recorded.